Scalable LED with improved current spreading structures

Abstract

An LED with improved current spreading structures that provide enhanced current injection into the LED's active layer, improving its power and luminous flux. The current spreading structures can be used in LEDs larger than conventional LEDs while maintaining the enhanced current injection. The invention is particularly applicable to LEDs having insulating substrates but can also reduce the series resistance of LEDs having conductive substrates. The improved structures comprise conductive fingers that form cooperating conductive paths that ensure that current spreads from the p-type and n-type contacts into the fingers and uniformly spreads though the oppositely doped layers. The current then spreads to the active layer to uniformly inject electrons and holes throughout the active layer, which recombine to emit light.

1. A scalable light emitting diode (LED) with enhanced current spreading structures, comprising:
 an LED core having: 
 an epitaxially grown p-type layer;  
 an epitaxially grown n-type layer; and  
 an epitaxially grown active layer between said p-type and n-type layers;  
 
 a first spreader layer adjacent to said LED core;  
 at least one groove through said LED core, to said first spreader layer;  
 a first contact having at least one first conductive finger on said first spreader layer within said at least one groove such that current flows from said first contact, into said at least one first conductive finger, into said first spreader layer, and into said LED core;  
 a second contact having at least one second conductive finger on said LED core opposite said first spreader layer such that current flows from said second contact into said at least one second finger and into said LED core.  
 
   
   
     2. The LED of  claim 1 , wherein said first spreader layer is an n-type epitaxial layer. 
   
   
     3. The LED of  claim 1 , wherein said n-type layer is adjacent to said first spreader layer. 
   
   
     4. The LED of  claim 1 , wherein said second contact and said at least one second conductive finger are on said p-type layer. 
   
   
     5. The LED of  claim 1 , wherein said at least one second conductive finger and said at least one first conductive finger are generally parallel for a portion of their lengths. 
   
   
     6. The LED of  claim 1 , wherein said at least one second conductive finger and said at least one first conductive finger are approximately uniform distance from one another for a portion of their lengths, to provide nearly uniform current injection into said LED core. 
   
   
     7. The LED of  claim 1 , further comprising a substrate adjacent to said first spreader layer, opposite said LED core. 
   
   
     8. The LED of  claim 7 , wherein said substrate is electrically conductive. 
   
   
     9. The LED of  claim 1 , further comprising a second spreader layer on said LED core opposite said first spreader layer, said second contact and said at least one second conductive finger disposed on said second spreader layer such that current applied to said second contact spreads to said at least one second conductive finger and throughout said second spreader layer, and into said LED core. 
   
   
     10. The LED of  claim 9 , wherein said second spreader layer is a transparent conductor. 
   
   
     11. The LED of  claim 9 , wherein said second contact and at least one second conductive finger form a generally U-shaped conductive path, said first contact and said first conductive finger forming an elongated conductive path within said U-shaped path. 
   
   
     12. The LED of  claim 9 , wherein said first contact and at least one conductive finger form a generally U-shaped conductive path, said second contact and said at least one second conductive finger forming an elongated conductive path within said U-shaped path. 
   
   
     13. The LED of  claim 9 , wherein said at least one first conductive finger and said at least one second conductive finger comprises a plurality of first and second conductive fingers, respectively, said second contact near one edge of said LED and said first contact near the opposite edge, said second conductive fingers forming a plurality of conductive paths from said second contact toward said opposite edge, said first fingers forming a plurality of conductive paths from said first contact toward said second contact interdigitated between said second fingers. 
   
   
     14. The LED of  claim 9 , wherein said at least one first conductive finger and said at least one second conductive finger comprises a plurality of first and second conductive fingers, respectively, said second contact is located near the center of said current spreading layer and said second conductive fingers form conductive paths from said second contact toward the edge of said LED, and said first conductive fingers form conductive paths from said first contact, toward said second contact interdigitated between said second conductive fingers. 
   
   
     15. The LED of  claim 9 , wherein said at least one first conductive finger and said at least one second conductive finger comprises a plurality of first and second conductive fingers, respectively, wherein said second contact is located in the center of said current spreading layer and further comprises two conductive branches forming conductive paths in opposite respective directions from said contact down a centerline of said LED, said second conductive fingers forming conductive paths generally orthogonal to said branches, said first conductive fingers forming conductive paths from said first contact and from the edge of said LED, toward said branches interdigitated between said second conductive fingers. 
   
   
     16. The LED of  claim 9 , wherein said at least one first conductive finger and said at least one second conductive finger comprises a plurality of first and second conductive fingers, respectively, wherein said second fingers form generally parallel zig-zag conductive paths from said second contact, and said first fingers form generally parallel zig-zag conductive paths from said first contact interdigitated between said second zig-zag fingers. 
   
   
     17. A scalable light emitting diode (LED) using flip-chip mounting and having enhanced current spreading structures, comprising:
 an LED core having: 
 an epitaxially grown p-type layer;  
 an epitaxially grown n-type layer; and  
 an epitaxially grown active layer between said p-type and n-type layers;  
 
 a first spreader layer adjacent to said LED core;  
 at least one groove through said LED core, to said first spreader layer;  
 a first contact having at least one first conductive finger on said first spreader layer within said at least one groove such that current flows from said first contact, into said at least one first conductive finger, into said first spreader layer and into said LED core;  
 a second spreader layer adjacent to said LED core, opposite said first spreader;  
 a conductive layer having two separate sections, a first section of said conductive layer bonded to said second spreader;  
 a submount adjacent to said first section of said conductive layer, opposite said second spreader, the second section of said conductive layer also adjacent to said submount, said LED further comprising a conductive material between said second section and said contact, a bias applied to said first and second sections of conductive layer causing said LED core to emit light.  
 
   
   
     18. The LED of  claim 17 , further comprising a substrate adjacent to said first spreader layer, opposite said LED core. 
   
   
     19. The LED of  claim 18 , wherein said substrate is made of a transparent or semi-transparent and is the primary emitting surface for the light generated by said LED core. 
   
   
     20. The LED of  claim 17 , wherein said second spreader layer is made of a semi-transparent material and further comprises a reflector to reflect light from the LED core toward said substrate. 
   
   
     21. The LED of  claim 17 , further comprising a bonding media between said conductive layer's first section and said second spreader, and wherein said conductive material comprising a bonding media.